U.S. patent application number 11/200441 was filed with the patent office on 2007-02-15 for low pressure anion chromatographic apparatus and method having two or more eluents.
This patent application is currently assigned to The Procter & Gamble Company. Invention is credited to Hiroshi Oh, Victorio Tan Wee, Xin-shen Zhang.
Application Number | 20070034572 11/200441 |
Document ID | / |
Family ID | 37441567 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070034572 |
Kind Code |
A1 |
Oh; Hiroshi ; et
al. |
February 15, 2007 |
Low pressure anion chromatographic apparatus and method having two
or more eluents
Abstract
A low pressure anion chromatography apparatus that includes a
first eluent reservoir that contains a first eluent, a second
eluent reservoir that contains a second eluent, and a valve for
switching flow between the first and the second eluent reservoirs.
The low pressure anion chromatography apparatus also has a low
pressure pump, an injector, an anion exchange column, and a
detector. The low pressure pump, the injector, the anion exchange
column, the detector and the first and second eluent reservoirs are
in fluid communication with one another through a series of fluid
conduits. A method of using the low pressure anion chromatography
apparatus is also provided. The use of two or more eluents allows
for a broader range of anions to be detected with a relatively
inexpensive low pressure chromatography system.
Inventors: |
Oh; Hiroshi; (Cincinnati,
OH) ; Wee; Victorio Tan; (Cincinnati, OH) ;
Zhang; Xin-shen; (Chengdu, CN) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;INTELLECTUAL PROPERTY DIVISION
WINTON HILL BUSINESS CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Assignee: |
The Procter & Gamble
Company
Cincinnati
OH
|
Family ID: |
37441567 |
Appl. No.: |
11/200441 |
Filed: |
August 9, 2005 |
Current U.S.
Class: |
210/656 ;
210/198.2; 422/70; 436/161 |
Current CPC
Class: |
B01D 15/363 20130101;
G01N 30/02 20130101; G01N 30/02 20130101; G01N 2030/645 20130101;
G01N 2030/385 20130101; G01N 30/96 20130101; G01N 30/38 20130101;
G01N 2030/965 20130101 |
Class at
Publication: |
210/656 ;
422/070; 210/198.2; 436/161 |
International
Class: |
B01D 15/08 20060101
B01D015/08 |
Claims
1. A low pressure anion chromatography apparatus comprising: a
first eluent reservoir containing a first eluent, a second eluent
reservoir containing a second eluent, and a valve for switching
flow between the first and the second eluent reservoirs; a low
pressure pump; an injector; an anion exchange column; a detector;
and wherein the low pressure pump, the injector, the anion exchange
column, the detector and the first and second eluent reservoirs are
in fluid communication with one another through a series of fluid
conduits.
2. The low pressure ion chromatography apparatus of claim 1,
wherein the anion exchange column analyzes for anions selected from
the group consisting of F.sup.-, NO.sub.3.sup.-, Cl.sup.-,
Br.sup.-, SO.sub.3.sup.2-, SO.sub.4.sup.2-, PO.sub.4.sup.3-,
P.sub.2O.sub.7.sup.4-, P.sub.3O.sub.10.sup.5- and mixtures
thereof.
3. The low pressure ion chromatography apparatus of claim 1,
wherein the first eluent is Na.sub.2CO.sub.3 at a concentration of
from about 1.0.times.10.sup.-5 mole/liter to about 1.0 mole/liter
and the second eluent is NaOH at a concentration of from about
1.0.times.10.sup.-2 mole/liter to about 0.5 mole/liter.
4. The low pressure ion chromatography apparatus of claim 1,
wherein the first eluent is NaOH at a concentration of from about
1.0.times.10.sup.-6 mole/liter to about 0.1mole/liter and the
second eluent is NaOH at a concentration of from about
1.0.times.10.sup.-6 mole/liter to about 0.5 mole/liter, and wherein
the concentration of the first eluent differs from the
concentration of the second eluent by at least about 50%,
preferably by at least about 80%, and more preferably by at least
about 100%, on a mole/liter basis.
5. The low pressure ion chromatography apparatus of claim 1,
wherein the anion exchange column is operated at a pressure of less
than about 500 psi and preferably less than 100 psi, and more
preferably from about 20 to about 50 psi.
6. The low pressure ion chromatography apparatus of claim 1, three
or more eluent reservoirs each containing a different eluent.
7. A method of analyzing anions in a fluid, the method comprising
the steps of: injecting a sample fluid into an a anion exchange
column; using a low pressure pump, pumping a first eluent through
the anion exchange column; switching from the first eluent to a
second eluent using a valve and pumping the second eluent through
the anion exchange column; and detecting the concentration of
various anions in the sample fluid with a detector.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus and method for
low pressure anion chromatography for the analysis of anions. The
present apparatus and methods employ an analytical procedure that
uses two or more different eluents that allows for the analysis of
more anions than in a conventional low pressure ion chromatography
system.
BACKGROUND OF THE INVENTION
[0002] In general, low pressure chromatography is a known art, and
there are many benefits to low pressure chromatography over high
pressure chromatography. But high pressure chromatography has one
distinct advantage, and that is, it allows for a broader range of
ions to be analyzed from one sample. More specifically, high
pressure chromatographic systems can measure more ions within a
given sample than a low pressure chromatography system can. Low
pressure chromatography has been limited by the affinity of certain
ions to the eluent used. That is, certain eluents allow for the
detection of some ions, but not all ions. And the low pressure
chromatography systems known to the art are all single stage
systems, that is, they employ only one eluent per sample. Thus, to
detect all of the ions in a given sample, it has been necessary to
test a given material multiple times with different eluents to
determine the existence and amount of all ions. This is a
labor-intensive process, and may even require multiple
chromatographic systems. And these problems are especially acute
when measuring anions.
[0003] A low pressure chromatography system for measuring cations
is described in U.S. Pat. No. 5,098,563, which issued to Zhang
Xin-shen, on Mar. 24, 1992. But the apparatus and method taught in
the Zhang Xin-shen patent is limited to the measurement of cations
and it is a single eluent system. Moreover, Zhang Xin-shen
published an article with Xiaoping Jiang, in the Journal of
Chromatography A, 671 (1994) 23-28, wherein the analysis of both
cations and anions is discussed. But none of the low pressure
hromatography systems described in these publications can analyze
for a broad range of ions in a single sample.
[0004] While high pressure systems, for example, those described in
the Journal of Chromatography A, 706 (1995) 199-207, by Umali et
al., solve some of the problems associated with low pressure
chromatography, high pressure systems have many disadvantages.
Specifically, because of the higher pressure of the chromatography
column and ancillary equipment, leakage often occurs around seals
and joints. Moreover, the cost of a high pressure system can by ten
times or more the cost of a low pressure system. This added cost is
due in part to the more sophisticated seals and joints, thicker and
higher quality materials of construction, and because high pressure
pumps are far more expensive than their low pressure counterparts.
Thus, low pressure chromatography systems are far less expensive,
less complicated and have fewer mechanical problems than high
pressure systems.
[0005] For these reasons there exists a need for improved low
pressure anion chromatography systems that can analyze for a broad
spectrum of anions while maintaining the economic and mechanical
benefits of a low pressure system. This need and others, are met by
the low pressure anion chromatography systems of the present
invention.
SUMMARY OF THE INVENTION
[0006] In one aspect, the present invention comprises a low
pressure anion chromatography apparatus comprising a first eluent
reservoir containing a first eluent, a second eluent reservoir
containing a second eluent, and a valve for switching flow between
the first and the second eluent reservoirs. The low pressure anion
chromatography apparatus further comprises a low pressure pump, an
injector, an anion exchange column, and a detector. The low
pressure pump, the injector, the anion exchange column, the
detector and the first and second eluent reservoirs are in fluid
communication with one another through a series of fluid
conduits.
[0007] In another embodiment of the present invention the anion
exchange column of the low pressure ion chromatography apparatus
analyzes for anions selected from the group consisting of F.sup.-,
NO.sub.3.sup.-, Cl.sup.-, Br.sup.-, SO.sub.3.sup.2-,
SO.sub.4.sup.2-, PO.sub.4.sup.3-, P.sub.2O.sub.7.sup.4-,
P.sub.3O.sub.10.sup.5- and mixtures thereof.
[0008] There is further provided herein a method of analyzing
anions in a fluid. This method comprises the steps of injecting a
sample fluid into an anion exchange column, using a low pressure
pump, pumping a first eluent through the anion exchange column,
switching from the first eluent to a second eluent using a valve
and pumping the second eluent through the anion exchange column;
and detecting the concentration of various anions in the sample
fluid with a detector.
[0009] The present methods and apparatuses provide a substantial
improvement over prior systems because a broader chromatogram of
anions can be detected in one sample using the low pressure
chromatography systems described herein. The present apparatuses
and methods have excellent precision and sensitivity, and can
detect anions in the parts per billion range. Moreover, the present
systems provide these advantages while maintaining all of the cost
and reliability advantages over high pressure chromatography
equipment. As such, the present apparatuses and methods provide
many unexpected and superior benefits over known low pressure anion
chromatography systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] While the specification concludes with claims particularly
pointing out and distinctly claiming the invention, it is believed
that the invention will be better understood from the following
description of preferred embodiments which is taken in conjunction
with the accompanying drawings in which:
[0011] FIG. 1 is a schematic representation of a low pressure anion
chromatography apparatus according to the present invention;
and
[0012] FIG. 2 is a chromatographic spectrum of anions analyzed by
the low pressure anion chromatography apparatus of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0013] As used herein, low pressure chromatography means
chromatography conducted in an anion exchange column at a pressure
of less than about 500 psi and preferably less than 100 psi, and
more preferably from about 20 to about 50 psi. The samples analyzed
by the low pressure anion chromatography apparatus described herein
form no part of this invention, but can include, for example,
laundry detergents, toothpaste, food, skin care products, hair care
products, and other consumer products that might comprise
anions.
[0014] Referring now to FIG. 1, which is a schematic representation
of a low pressure anion chromatography apparatus 10 according to
the present invention. Low pressure anion chromatography apparatus
10 comprises a first eluent reservoir 12, a second eluent reservoir
14, a switching valve 16, a low pressure pump 18, a sample injector
20, an anion exchange column 22, a suppressor 24, a flow
conductivity cell 26, a conductivity detector 28, and a workstation
30. First eluent reservoir 12 contains first eluent 32 and second
eluent reservoir 14 contains second eluent 34. The majority of the
component parts of low pressure anion chromatography apparatus 10
are in fluid communication with one another via fluid conduits 13.
Workstation 30 is in electrical communication with conductivity
detector 28 via electrical cable 15.
[0015] During operation, low pressure pump 18, pumps eluent from
either first eluent reservoir 12 or second eluent reservoir 14 into
anion exchange column 22. Switching valve 16 controls which of the
eluent reservoirs is in use. While eluent is flowing through anion
exchange column 22, a sample fluid is injected into column 22 by
sample injector 20. Both the sample and the eluent travel through
the column and before the sample has completely passed through the
column, switching valve 16 switches the flow from one eluent to the
other. The time that this switch takes place will depend on various
factors, for example the flow rate of the eluent, the size of the
sample, the size of the column, and the like. But the time that the
switch should take place will be quite evident to those skilled in
the art. When anions are no longer being detected with the first
eluent, then it is time to switch to the second eluent.
[0016] More specifically, as the sample and the eluent flow
together through column 22 they react chemically in a manner that
separates the anions from their associated cations.
[0017] While still in solution, the anions flow from column 22 to
suppressor 24, and then onto flow conductivity cell 26 and
conductivity detector 28, which work in tandem to produce an
electrical detection signal related to each anion detected.
Suppressor 24 is used to help eliminate the strong signal
associated with the large concentration of anions from the eluent
such as OH.sup.-. The detection signal is sent to work station 30
where it can be displayed, printed, stored on an electronic medium
or transferred to other electronic devices.
[0018] Eluents that are appropriate for use in the present low
pressure chromatography systems include, but are not limited to,
Na.sub.2CO.sub.3, and NaOH. Preferably, first eluent 32 is
Na.sub.2CO.sub.3, at a concentration of from about
1.0.times.10.sup.-5 mole/liter to about 1.0 mole/liter and second
eluent 34 is NaOH at a concentration of from about
1.0.times.10.sup.-6 mole/liter to about 0.5 mole/liter. Although
the first and second eluents can be different chemical composition,
they can also be the same chemical composition but in different
concentrations. For example, the first eluent can be NaOH at a
concentration of from about 1.0.times.10.sup.-6 mole/liter to about
0.1 mole/liter and the second eluent can be NaOH at a concentration
of from about 1.0.times.10.sup.-2 mole/liter to about 0.5
mole/liter. When the first and second eluents are the same chemical
composition it is preferred that the concentration of the first
eluent differ from the concentration of the second eluent by at
least about 50%, preferably by at least about 80%, and more
preferably by at least about 100%, on a mole/liter basis. It is
understood that three or more different eluents can be used with
the low pressure chromatography apparatuses and methods disclosed
herein. "Different eluents" as used herein means that each eluent
is a different chemical composition or the eluents can be the same
chemically and differ in their respective concentrations. While the
drawings and much of the description focuses on a low pressure
chromatography system having only two eluents, the present
invention is not so limited.
[0019] Retuning again to FIG. 1, wherein eluent reservoirs 12 and
14 can be any appropriate size and made of any material that can
contain and is compatible with first eluent 32 and second eluent
34. As used throughout the following description of the component
parts of low pressure anion chromatography apparatus 10, compatible
materials include, but are not limited to, rubber, plastic, glass,
metal, and the like.
[0020] Materials that resist corrosion, for example stainless
steel, poly vinyl chloride, polyethylene, polypropylene, and Teflon
are preferred. For example, eluent reservoirs 12 and 14 can be
polyethylene bottles with a volume of from about 100 ml to about 10
liters. Such reservoirs are commonly available from chemical
suppliers, such as Dionex Corporation. Likewise, switching valve 16
can be any flow regulating device that is compatible with the first
and second eluents, and can stop the flow of one eluent while
starting the flow of the other eluent. Preferably, switching valve
16 is automated, that is it automatically switches from one eluent
to another based on a predetermined criteria. The predetermined
criteria can be, for example, a set period of time, a preselected
volume of one eluent, or a signal from the detector after a
preselected anion has been detected. Switching valves are known,
and examples include model SV2 manufactured by Laboratory of
Analytical Equipment, Sichuan University, Chengdu, China, and model
SV-3 valve manufactured by BIO-RAD Laboratories, Hercules, Calif.,
USA.
[0021] Low pressure pump 18 should be compatible with first eluent
32 and second eluent 34, and such pumps are known to the art and
commercially available, for example, models LDB-M and LDB-H
electronic peristaltic pumps manufactured by Dingshan Instrument
Factory in Xiangshai Country, Zhejiang Province, PRC, and Bio Logic
LP system manufactured by BIO-RAD Laboratories, Hercules, Calif.,
USA.
[0022] Injector 20, anion exchange column 22, suppressor 24, flow
conductivity cell 26, and conductivity detector 28 should all be
compatible with first eluent 32, second eluent 34, as well as the
sample fluid (not shown). Injectors will be known to those skilled
in the art and examples include model AJ1 manufactured by
Laboratory of Analytical Equipment, Sichuan University, Chengdu,
China, and model MV-6 injection valve manufactured by BIO-RAD
Laboratories, Hercules, Calif., USA.
[0023] Columns suitable for use herein can be any appropriate size
depending on the amount of sample material that will be analyzed,
the flow rate of the eluents etc. Suitably sized columns can have
an internal diameter of from about 0.2 cm to about 3 cm, with a
height of from about 3 cm to about 30 cm, and a volume of from
about 0.5 mili-liters to about 850 mili-liters. An example of a
column that is appropriate for use as anion exchange column 22 in
conjunction with low pressure anion chromatography apparatus 10 is
C2 Anionic Exchange Column manufactured by Laboratory of Analytical
Equipment, Sichuan University, Chengdu, China. The column is packed
with and ion exchange resin that can be, for example,
tetrabutylamonium salt. Other packing and resins will be known to
those skilled in the art. An example of a suppressor is Anion
Self-Regenerating suppressor ASRS manufactured by Dionex
Corporation, Sunnyvale, Calif., USA. Examples of flow conductivity
cells that are appropriate for use in the present low pressure
anion chromatography apparatus include model CC1 manufactured by
Laboratory of Analytical Equipment, Sichuan University, Chengdu,
China, and model DS3 manufactured by Dionex Corporation, Sunnyvale,
Calif., USA. Examples of conductivity detectors that are
appropriate for use in the present low pressure anion
chromatography apparatus include model CD1 manufactured by
Laboratory of Analytical Equipment, Sichuan University, Chengdu,
China, and model CD20 manufactured by Dionex Corporation,
Sunnyvale, Calif., USA.
[0024] Fluid conduits 13 connect many of the various component
parts of a low pressure anion chromatography apparatus 10. The
conduits can be made of any compatible material as discussed above,
and should be sized to achieve the desired flow rates through the
various components. The individual sections of fluid conduit 13 can
be made of different materials or they can all be the same. The
selection of the fluid conduits and their materials of construction
is within the skill of an artisan in the analytical chemical
field.
[0025] Workstation 30 can be any electronic device capable of
receiving signals from conductivity detector 28 and converting that
signal into a detection output. The output can be stored directly
into memory, relayed to a printing device, or visual monitor, or it
can be used to regulate the flow of eluents as discussed above.
Regardless, workstation 30 can be, for example, an IBM Personal
Computer 350 with the software Model LPIC 1 manufactured by
Laboratory of Analytical Equipment, Sichuan University, Chengdu,
China.
[0026] The following is a non-limiting example of a low pressure
anion chromatography apparatus and method according to the present
invention.
EXAMPLE I
[0027] Five laundry detergents are analyzed with a low pressure
anion chromatography apparatus as described herein. Each of the
detergents is dissolved in water to form a 1%, by weight, solution.
The first eluent is Na.sub.2CO.sub.3 at a concentration of
1.0.times.10.sup.-3 mole/liter, and the second eluent is NaOH at a
concentration of 8.0.times.10.sup.-2 mole/liter. The anionic
exchange column is operated at between 30 and 50 psi and the
electric conductivity detector is set at 2 mv.
[0028] For each of the five tests, the eluent flows through the
column at 1.2 ml/minute. 20 .mu.l of the 1% detergent sample is
injected into the eluent. The results of the tests are given in
Table 1 below. Moreover, FIG. 2 is a chromatographic spectrum of
anions analyzed from Detergent B. As can be seen in FIG. 2, shortly
after the sulfate anions are detected the first eluent is stopped
and the second eluent is pumped through the column. Without the
second eluent, the diphosphate (P.sub.2O.sub.7.sup.4-) and
triphosphate (P.sub.3O.sub.10.sup.5-) anions would not be detected.
TABLE-US-00001 SO.sub.4.sup.2- PO.sub.4.sup.2- PO.sub.4.sup.2-
PO.sub.4.sup.2- Detergent Wt. % Wt. % Wt. % Wt. % A 31.1 0.3 1.4
16.7 B 35.2 1.0 5.0 15.5 C 37.7 1.0 4.6 14.0 D 25.0 1.3 5.0 11.5 E
35.5 1.3 3.2 21.6
[0029] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any meaning or definition of a term in this written
document conflicts with any meaning or definition of the term in a
document incorporated by reference, the meaning or definition
assigned to the term in this written document shall govern.
[0030] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *